All this pay-as-you-go BS is such a scam (note: I'm not blaming victims here.) There's just so many ways to screw you. Like a program gets bug and starts sending out a metric crap load of traffic. Or you get DDoSed and charged for the bandwidth. Or your disk fills up from log file spam, it gets 'backed up', you get charged for it. Or a program is caught in a loop and uses limited CPU usage.
I think its all hiding the fact that people don't want to take the time to design (and maintain) scalable infrastructure and instead rely on fake abstractions that pretend to be infinite, always-available, magic, or w/e. I'm sure there is some open source software that helps here.